Preheat the oven to 250 degrees. Combine the ingredients for the Homemade Seasoned Salt in small bowl then set aside.
To a very large mixing bowl, add the Rice Chex, Corn Chex, O's cereal, and peanuts then set aside.
To a medium-sized mixing bowl or cup, add the butter then microwave until melted, 60 seconds or so. Add the worcestershire sauce plus 2 teaspoons Homemade Seasoned Salt (again, you WILL NOT USE ALL the seasoned salt!) then stir to combine.
Pour the butter mixture over the cereal mixture then stir with a spatula to evenly coat. Pour the mixture into a 11x17" or larger baking dish then bake for 45 minutes to 1 hour, stirring every 15 minutes, or until the cereals are light golden brown. Stir in the pretzels then cool and serve.
Notes
If you are typically sensitive to salt, cut the seasoned salt amount down to 1-1/2 teaspoons.